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THE PRODUCTIGN OP VOLATILE FATTY ACIDS

IN SHE!-;}) ON DIFFERENT PASTURE 'l'YPES

A thesis presented 1n partial tultilment ot the

requirements tor tbe degree ot Maeter

ot Agricultural Science in Antmal Science

a·t Maase)' Uu1vers1 t7

J AJJ.ES BRUCE MACKINTOSH

1970

AODOWLEDGEMEirfS

I wlab to �ank my supervisors, Dr. M.J.Ulyatt end

Proteasor D.s.nux, tor tbetr continual Interest, guidance

and asslatance thro�gbout tn1• proJect.

I indebted � the following tor their valuable and

w1111DS aaa1atanoe:

1lr P.Vlleg and tbe tecbn1cal atatt ot the Applied

Btoob let� Dlvialon, D.S.I.R. tor tbe prep ration

101d care ot the anlm8la;

Mr B.A.Tbomaon and Mr A.S.D.KlDg tor technical

aaslatance durlDg the experimot;

Mr J.A.Raven, Kr I.D.Sbelton and Mr N.J.Cbandler tor

aaeistance wltb obemical anal7als ot pasture;

The atatf ot the Herbage Laboraloey, Gr aalmda

Dlvlalon, D.S.I.R. tor tbe botanical anal7aea;

M bera ot the Sheep and Dalr,r Huabandr7 Departmenta

tor belptul dlacu .. lon.

Special tbanka are due to Kre M.D.Bew\b tor t7P1DB tb1a

theala.

PREP ACE

'rhe New Zealand economy depends largely on the

ettlclent conversion ot pasture to exportable animal products.

The current emphasis on higher stocking rates increases the

need tor pastures best suited to animal production.

Pasture species used 1D New Zealand are recognised

as ditter1ng in their ettects on animal production, these

differences being loosely attributed to Yariation 1n�asture

quality". It the level ot oatput ot saleable product la

the accepted measure ot pasture quality, thea the principal

factors governing this are the quantity ot teed consumed

and its subsequent ut111aat1on.

A number of studlea hRve shown that dltterences ln

food intake alone cannot account tor the observed differences

ln antmal performance. It baa thus been considered important

to investigate the factors attectlng the utlliaatlon ot

pasture by the animal.

Volatile tatty acids (VFA) produced ln the rumen

are generally considered to account tor 10 to 80 per cent

ot the net energy requlrementa ot ruminants, and their

production must be a ••Jor dete�lnant ot teed utlllaation.

Dltterences 1D tbe ruminal oonoentrationa and proportloaa ot

VPA have ott.en ben obaerYecl wl'tb pasture teedlDg and have

been otted aa poaalble reaaona tor dltterenoea 1D pasture

qual1t,-.

Tbe lnveat1sat1oa deaor1bed bere waa undertaken a a

prellm1D&r7 atudy ot tbe role ot VPA production lD determining

tbe quall� ot ••• Zealand p sture speolea.

TABLE OF CONTENTS

CHAPTER ONE REVIEW OP LITERATUHE

Introduction 1

1.1. The Quality ot M Jor New Zealand Paature Speolea 2

1.2. The Nutritional Slgn1t1canoe ot Volatile Patty Acid 6

1.3. Teobnlquea tor the �eaeurement ot VPA Production Rete 22

1.4. Sampling trom the : umen ot the Sb ep 36

CHAPTER TWO MAT�:aL\LS AND MF.THODS

2. 1. Animal a 41

2.2. Paatures 42

2.3. Experimental Dealgn 43

2. 4. Peed Organ1aat1on 45

2. 5. Apparent Dtg at1b111ty Determination 46

2.6. Intu ton Techn1qu 47

2. 7. V.A Sampllng Proo dure 48

2.8. ADalyttcal ethoda 51

2.9. St tt tloal AD l7a1a ot Dat 59

CHAPTER THREE

3.2.

CHAPTER FOUR

4.1.

4.2.

4.3.

RESULTS

lxper1mentel Method

Animal

Pastures

Dige tibl Energy Intake

VFA Infusion

VFA Sampling and An lyeia

VFA Production Rotee

The Contribution of VJA ProduotloD to Digestible Energv Intake

DISCUSSION

VFA Produotion RBtee

The Rel tionehlp between V?A Conoentr tion nd VPA Production 1n tb Rumen

The Mea•urement of V?A Production 1n tbe Rumen ot Graslng Sbe p

SUMUARY

REFlm.ENCES

APPJmDICBS

60

66

67

69

71

72

75

n

78

82

84

87

89

Table

1.1.

1.2.

1. 3.

1.4.

1. 5.

2.1.

2.2.

3.1.

3.2.

3. 5.1.

3.6.

3.7.

LIST OF' T.I\BI.ES

Live Weight Gains of Sheep on Different Pasture Species

Rumen Characteristics ot Sheep on Different Pasture Species

Published Estimates of VFA Production in Sheep

Theoretical Ktfic1ency of Utilisation ot Various Subatrates

Interconversion of VFA in the Rumen ot Sheep

General Plan ot the F�periment

Analysts of Total Soluble Sugars

Analysis uf Regression of VFA Proportions in D1alysstcs on Proportions in Prepared Solutions

Molar Proportions ot VFA in Rumen Samples

Analysts ot Regression ot VP.A. Proportions in Dialysates on Proportions in Direct Samples

Recovery of 14c Label after Preparation tor Counting

Live Weights and Live �eight Changes ov er the Experimental Period

Botanical Composition ot Pastures

Chemical Composition and Energy Content ot Herbage

Soluble Carbohydrate Content ot Cut Feeds

following page

2

3

7

page 13

34

43

51

60

61

61

page 62

66

page 67

67

page 68

3.8.

3.10.

3.1 1 .

3.12.

3. 1 3.

3.14.

�. 1 5.

3.1 6.

Mean D lly Intakes and D1geet1b111ty ot Pest�res. Period I

Mean Daily Intakes end D1gest1b111ty ot Paaturee. Period II

Digestible Energy Intakes

Molar Proportion or VFA in D1alyaatea

Percentages ot Total 14c 1n _ oh Hum n Acld

Recovery of Rad1oact1v1ty 1n Rumen VFA during Intrarum1nal Infusion ot Labelled Acetic Acid

Interoonvers1on ot VFA in the Rumen

VPA Production Uetes

Contr1bli tion ot V�A Production to DE Intake

68

68

page 69

72

72

page 73

73

75

77

Figure

1.1.

1. 2.

3.1.

LIST OF FIGURES

Metabolic Pathways ot VFA Production

Metabolic Pathways of VFA Utilisation

Relationship between Channels Retio and Counting Efficiency

following page

6

13

64

Plate I

Plate II

Plate III

LIST OF PLA'l'ES

Infusion and Sampling Apparatus in Operation

Diagrammat1o Representation ot Dialysis Probe

Relative Positions ot Diely is Probe and Intus1on Outlet

following page

47

48

Appendix I

Appendix II

Appendix III

Appendix IV

Appendix V

Appendix VI

Appendix VII

Appendix VIII

Appendix IX

Appendix X

Appendix XI

APPENDICES

Live Weight Changes - AD ly sis ot Variance

Dig stible ergy Intake - Analysis of Ver1anoe

Rate ot Infusion ot 14c-Labelled VFA

Measurement o f Specific Act1v1ty ot Infusion Solutions - Analy 1s of Variance

Specific Aot1v1t1es ot Rumen VFA Samples

Measurement ot Specific Activity ot Rumen VFA trom separated Acids - Analysis ot Variance

Measurement of Spec1tic Activity ot Total Rumen VFA - Analy•is ot Variance

Elimination of Spurious Results

Example Calculation ot VFA Prod uction

Rete and Contribution to DE Intake

Production Rates ot VFA - .Analy la ot Variance

Contribution ot VPA Production to DE Intake - ADaly i or Variance